2-[1-cyanopropyl)carbamoyl]-5-chloromethyl nicotinic acids and the use thereof in manufacturing herbicidal imidazolinones

ABSTRACT

2-[(1-cyanopropyl)carbamoyl]-5-chloromethyl nicotinic acids of formula (I) where Z is hydrogen or halogen; Z 1  is hydrogen, halogen, cyano or nitro; R 1  is C 1 -C 4  alkyl; R 2  is C 1 -C 4  alkyl, C 3 -C 6  cycloalkyl or R 1  and R 2 , when taken together with the atom to which they are attached, represent a C 3 -C 6  cycloalkyl group optionally substituted with methyl, and R 3  is hydrogen or a cation preferably selected from the group consisting of alkali metals, alkaline earth metals, manganese, copper, iron, zinc, cobalt, lead, silver, nickel, ammonium and organic ammonium; are useful intermediates for the synthesis of herbicidal imidazolinones.

This application is a National Stage application of InternationalApplication No. PCT/EP2009/064495, filed Nov. 3, 2009, which claims thebenefit of U.S. Provisional Application No. 61/114,238, filed Nov. 13,2008, the entire contents of which are hereby incorporated herein byreference.

The invention relates to 2-[(1-cyanopropyl)carbamoyl]-5-chloromethylnicotinic acids, the preparation of these compounds and their use inmanufacturing herbicidal imidazolinones, such as imazamox.

Derivatives of 2-(2-imidazolin-2-yl)nicotinic acids, like imazamox(2-[(RS)-4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl]-5-methoxymethylnicotinic acid),

are useful selective herbicides which act as ALS-inhibitors and can beused in pre- and post-emergence applications.

Various processes for the synthesis of these compounds are known fromthe literature, see e.g. EP-A 0 322 616, EP-A 0 747 360, EP-A 0 933 362or Q. Bi et al, Modern Agrochemicals 6(2)(2007) 10-14.

Although synthesis on an industrial scale is carried out by thesemethods there is still room for improvement, specifically in view ofeconomical and ecological aspects, such as overall yield improvement orthe avoidance of certain solvents or reagents.

EP-A 0 322 616 discloses the synthesis of2-[(1-carbamoyl-1,2-dimethylpropyl)carbamoyl]-5-chloromethyl nicotinicacid by reaction of 5-chloromethyl-2,3-pyridine dicarboxylic acidanhydride with α-amino-α-methylvaleramide and further conversion of thiscompound to imazamox by reaction with NaOCH₃ and subsequentacidification.

One task of the invention is to provide new useful intermediates for thesynthesis of herbicidal imidazolinones, and a process for theirpreparation. A further task of the invention is to provide an improvedprocess for manufacturing herbicidal imidazolinones, like imazamox.

It has been found that 2-[(1-cyanopropyl)carbamoyl]-5-chloromethylnicotinic acids are useful intermediates in the manufacture ofherbicidal imidazolinones.

EP-A 0 184 027 and EP-A 0 144 595 describe the reaction ofpyridine-2,3-dicarboxylic acid anhydrides with2-amino-2,3-dimethyl-butyronitrile and further conversion to herbicidalimidazolinones, however, no examples for 5-chloromethyl substitutedcompounds are disclosed.

Accordingly, in one aspect of the invention there is provided a2-[(1-cyanopropyl)carbamoyl]-5-chloromethyl nicotinic acid of formula(I),

where

-   Z is hydrogen or halogen;-   Z¹ is hydrogen, halogen, cyano or nitro;-   R¹ is C₁-C₄ alkyl;-   R² is C₁-C₄ alkyl, C₃-C₆ cycloalkyl or R¹ and R², when taken    together with the atom to which they are attached, represent a C₃-C₆    cycloalkyl group optionally substituted with methyl, and-   R³ is hydrogen or a cation preferably selected from the group    consisting of alkali metals, alkaline earth metals, manganese,    copper, iron, zinc, cobalt, lead, silver, nickel, ammonium and    organic ammonium.

In another aspect of the invention there is provided a process forpreparing a 2-[(1-cyanopropyl)carbamoyl]-5-chloromethyl nicotinic acidof formula (I), comprising the step of

-   (i) reacting a 5-chloromethyl-pyridine-2,3-dicarboxylic acid    anhydride of formula (II),

where Z, Z¹ are as in formula (I),with a 2-aminoalkane carbonitrile (III),H₂N—CR¹R²—CN  (III)where R¹ and R² are as in formula (I).

In a further aspect of the invention there is provided the use of acompound of formula (I) for preparing a herbicidal imidazolinone offormula (IV),

whereinZ, Z¹, R¹, R², R³ are as defined in formula (I).

In a further aspect of the invention there is provided a process forpreparing a herbicidal imidazolinone compound of formula (IV),

comprising the steps of:

-   (i) hydrolyzing the nitrile of formula (I) to obtain an amide of    formula (V),

whereZ, Z¹, R¹, R², R³ are as defined in formula (I); and

-   (ii) reacting compound (V) with CH₃OM or MOH/CH₃OH (where M is    alkali metal, preferably Na or K), optionally followed by    acidification to form the herbicidal imidazolinone (IV).

The use of the novel intermediate (I) in the synthesis of herbicidalimidazolinones leads to an improved yield in preparing amide (V) and,thus, in the overall yield of the synthetic process. Theregioselectivity of the opening of the anhydride is excellent evenwithout the addition of the nitrogen bases recommended in EP-A 0 144595.

In formula (I) the symbols preferably have the following meanings:

-   Z is preferably hydrogen.-   Z¹ is preferably hydrogen.-   R¹ is preferably C₁-C₄ alkyl.-   R² is preferably C₁-C₄ alkyl.-   R³ is preferably hydrogen, alkali metal or NR⁴R⁵ ₃, where R⁴ is    hydrogen or R⁵, and R⁵ is C₁-C₄ alkyl.

Preferred are compounds of formula (I) where all symbols have thepreferred meanings.

A particularly preferred compound of formula (I) is compound (Ia):

and salts thereof.

Compound (I) can be prepared by reaction of anhydride (II) withaminonitrile (III) as exemplified by the synthesis of preferred compound(Ia), where R¹ and R² are defined as in formula (III):

Aminonitriles (III) are commercially available or can be prepared bymethods known in the art. Generally 0.8 to 1.2 equivalents aminonitrile(III) per equivalent of compound (II) are used, preferably 0.95 to 1.1.

The reaction is carried out in a solvent, which is preferably selectedfrom aromatic hydrocarbons, preferably toluene, mesitylenes, chlorinatedaromatic hydrocarbons, such as chlorobenzene, dichlorobenzenes,chlorinated aliphatic hydrocarbons, such as 1,2-dichloroethane anddichloromethane, acetic acid, and mixtures thereof.

If acetic acid is not used as the main solvent, addition of 0.5 to 10equivalents, preferably 1 to 3 equivalents (based on compound (II)), isadvantageous.

Further advantageous additives that improve the selectivity of thering-opening reaction (2 versus 3 position) are listed in U.S. Pat. No.4,562,257, and comprise pyridine, 4-picoline, 2-picoline and quinoline.However, although these additives can be used, according to theinvention it is not necessary to employ such additives, and in oneembodiment, the listed additives are not present in the reactionmixture.

The reaction is generally carried out at a temperature range of fromabout 40 to about 120° C., preferably of from about 60 to about 100° C.The reaction time is generally from about 1 to about 3 h.

In a preferred embodiment compound (II) is dissolved in the solvent andbrought to the reaction temperature, and aminonitrile (III) is graduallyadded. After completion of the reaction and cooling, nitrile compound(I) can be isolated by standard methods.

In a further preferred embodiment, however, compound (I) is not isolatedbut the reaction mixture is directly used for the followinghydrolyzation of the nitrile.

In a preferred embodiment of the invention the anhydride (II) that isused in the preparation of compound (I) is obtained by a processcomprising the steps of

-   (i) reacting a compound of formula (VI),

wherein the symbols have the meaning given in formula (I), with achlorinating agent, optionally in the presence of a radical initiator ina solvent selected from halogenated hydrocarbons, preferably fromdichloroethane, chlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene,1,4-dichlorobenzene and tetrachloromethane, and

-   (ii) crystallization of the compound (II) formed in step (i) from a    solvent selected from 1,2-dichloroethane, chlorobenzene,    1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene,    trichloromethane, dichloromethane, toluene, xylenes, mesitylenes,    alkyl acetates (e.g. ethyl acetate, butyl acetate, methyl acetate),    methyl tert.-butyl ether, diisopropylether, cyclopentyl methyl    ether, and mixtures thereof.

Compounds of formula (V) and their preparation are known, e.g. from EP-A0 933 362.

Suitable chlorinating agents include chlorine, sulfurylchloride,N-chlorosuccinimide, and trichloroisocyanuric acid. Preferredchlorinating agents are chlorine and sulfurylchloride (SO₂Cl₂).

The molar ratio of pyridine compound (VI) to chlorinating agent isgenerally in the range of 1:0.5-1.5, preferably 1:0.7-1.2, morepreferably 1:0.8-1.1.

Suitable free-radical generators for initiating the reaction are thosewhich decompose at the selected reaction temperature, i.e. both thosewhich decompose by themselves and those which do so in the presence of aredox system. Examples of preferred initiators are free-radicalgenerators, such as azo compounds and peroxides. It is also possible,however, to use redox systems, especially those based on hydroperoxides,such as cumene hydroperoxide. Light induced chlorination withoutaddition of an initiator is also possible.

Radical initiators suitable for use in the method of the inventioninclude 2,2′-azobisisobutyronitrile (AIBN),2,2′-azobis(2-methylbutyronitrile),2,2′-azobis(2,4-dimethyl-pentanenitrile),1,1′-azobis(cyclohexanecarbonitrile), organic and inorganic peroxidessuch as dilauroyl peroxide, hydrogen peroxide, benzoyl peroxide and thelike, with 2,2′-azobisisobutyronitrile,2,2′-azobis(2-methylbutyronitrile) and dilauroyl peroxide beingpreferred, and 2,2′-azobisisobutyronitrile being particularly preferred.

Preferably the initiator is added continuously over the course of thereaction.

The molar ratio of initiator to chlorinating agent is preferably in therange of 0.001-0.1:1, more preferably 0.002-0.05.

Organic solvents for step (i) are halogenated hydrocarbons, preferablychlorinated hydrocarbons, more preferably chlorinated aliphatic oraromatic hydrocarbons. Strongly preferred are solvents selected fromchlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene,1,4-dichlorobenzene, 1,2-dichloroethane and tetrachloromethane,preferably 1,2-dichlorobenzene, 1,3-dichlorobenzene,1,4-dichlorobenzene, 1,2-dichloroethane and chlorobenzene. Chlorobenzeneis particularly preferred. The term solvent as used herein includesmixtures of two or more of the above compounds. In addition the termcomprises solvents that contain up to 20% by weight, preferably up to10% by weight, in particular up to 5% by weight of further solventswhich are not halogenated hydrocarbons.

The amount of organic solvent may vary to a large extent. Preferably 250g to 1500 g, more preferably 500 g to 1000 g, of organic solvent per molof compound (V) are employed.

In one preferred embodiment (where the chlorinating agent is a liquid)step (i) is carried out by dissolving compound (VI) in the organicsolvent, heating, and slowly adding a solution of the initiator in thechlorinating agent. After completion of the reaction the solvent ispartly or completely distilled off, and the mixture is slowly cooleddown to precipitate the product.

In a further preferred embodiment compound (VI) is dissolved in thesolvent, and gaseous chlorine is charged to the reaction vessel orpassed through the solution. After completion of the reaction thesolvent is at least partly distilled off to remove excess chlorine andgaseous byproducts such as HCl. The reaction mixture is then cooled downand compound (II) is precipitated.

In a further preferred embodiment reaction (step (i)) is carried out asa continuous operation.

If chlorine is used as chlorinating agent the reaction is generallycarried out at a temperature of about 0° C. to about 160° C., preferablyabout 60° C. to about 140° C., particularly preferred about 80° C. toabout 120° C.

If a liquid chlorinating agent is used, in particular sulfurylchloride,the reaction is generally carried out at a temperature of about 0° C. toabout 140° C., preferably about 50° C. to about 120° C., particularlypreferred about 70° C. to about 90° C.

The reaction may be carried out under atmospheric pressure or underelevated pressure of up to 6 bar, preferably up to 2 bar. Elevatedpressure is preferred if chlorine is used as chlorinating agent.

The reaction time (for step (i)) differs with the reaction parametersbut is generally between 5 min and 300 h. In case of a continuousreaction the residence time in the reaction vessel is preferably in therange of 2 to 10 minutes, in particular about 5 minutes.

In step (ii) of the reaction compound (II) is crystallized from asolvent selected from chlorobenzene, 1,2-dichlorobenzene,1,3-dichlorobenzene, 1,4-dichlorobenzene, 1,2-dichloroethane,trichloromethane, toluene, xylenes, mesitylenes, ethyl acetate, butylacetate, methyl acetate, methyl tert.-butyl ether, diisopropyl ether,cyclohexyl methyl ether, and mixtures thereof.

The term solvent as used herein includes solvent mixtures.

Chlorobenzene and the dichlorobenzenes are preferred, chlorobenzene isparticularly preferred.

It is possible that the solvent used for crystallization comprised up to90% by weight, preferably from 10 to 80% by weight, in particular 20 to60% by weight of an anti-solvent, i.e. a liquid in which the compound offormula (I) is essentially insoluble, such as aliphatic hydrocarbons,like n-hexane, hexanes, or cyclohexane.

Crystallization is generally carried out at a temperature in the rangefrom about −40° C. to 30° C., preferably about 0° C. to about 20° C. Theconcentration of compound (I) in the solvent from which it iscrystallized is generally in the range of from 5 to 60% by weight,preferably 10 to 50% by weight.

Crystallization can be carried out by standard methods, e.g. by coolingof a saturated solution of compound (II), by seeding with pure compound(I), by adding an anti-solvent, or by a combination of these methods.

According to the invention compound (II) must be at least oncecrystallized from one of the above listed solvents or a mixture of twoor more of these solvents.

In a preferred embodiment of the invention the chlorination of step (i)is carried out in a solvent which can be used for the crystallization ofstep (ii). Preferably compound (II) is then crystallized from thereaction mixture after the completion of step (i).

Optionally the original solvent may be partially (or completely)distilled off, and it is also possible to add further solvent, e.g. tocompensate for solvent that was distilled off.

It is further preferred to recrystallize compound (II) once or more,preferably once, to improve the purity of the product. Recrystallizationis usually carried out in the same solvent as the initial solvent, butof course it is also possible to use a different solvent or solventmixture from the listed group.

The mother liquor of a recrystallization is preferably recycled to thefirst crystallization step to minimise yield losses.

In a further preferred embodiment of the invention the chlorination ofstep (i) is carried out in a solvent which is different from thesolvents used for the crystallization of step (ii). In this embodimentthe solvent of step (i) is removed, and raw compound (I) is dissolved ina solvent of step (ii) and crystallized. One or more re crystallizationsteps with the same or different solvents are or course possible, andmother liquor can be recycled as stated above.

It is preferred that the same solvent is used in step (i) and (ii), inparticular chlorobenzene or dichlorobenzene.

The purity of compound (I) after re crystallization, determined by HPLC(after quench of the analyt with methanol), is preferably at least 95%,more preferably at least 98%.

Isolation of compound (II) after (re) crystallization can be carried outby standard methods, e.g. by filtration, washing with a suitable solventand drying.

Compound (II) prepared as described above is particularly useful for thesynthesis of the inventive intermediate (I) because of its purity.Therefore, in a preferred embodiment the process for preparing compound(I) comprises the steps of

-   (i-1) reacting a compound of formula (VI),

wherein the symbols have the meaning given in formula (I),with a chlorinating agent, optionally in the presence of a radicalinitiator, in a solvent selected from halogenated hydrocarbons, and

-   (i-2) crystallizing the compound (II) formed in step (i) from a    solvent selected from 1,2-dichloroethane, chlorobenzene,    1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene,    trichloromethane, dichloromethane, toluene, xylenes, mesitylenes,    alkyl acetates (e.g. ethyl acetate, butyl acetate, methyl acetate),    methyl tert.-butyl ether, diisopropylether, cyclopentyl methyl    ether, and mixtures thereof, to obtain anhydride (II), and-   (i-3) reacting anhydride (II) with a 2-aminoalkane carbonitrile    (III),    H₂N—CR¹R²—CN  (III),    -   where R¹ and R² areas in formula (I).

The compounds of formula (I) are useful intermediates in the synthesisof herbicidal imidazolinones (IV).

In a first step the nitrile function is hydrolyzed to yield therespective amide (V) as exemplified with preferred compounds (Ia) and(Va):

In a typical procedure a slight excess (e.g. 1.1 to 1.5 equivalentsbased on (I)) of a strong mineral acid, preferably sulfuric acid(preferably in a concentration of 30 to 98%) and water (e.g. 2 to 10equivalents) are added at a temperature which is generally in the rangeof about 30° C. to 120° C., preferably 50° C. to 90° C. The mixture isfurther stirred until complete conversion. The reaction time isgenerally from 1 to 8 h, preferably 1 to 5 h.

Workup and isolation can be achieved by standard methods, such asprecipitation from an aqueous solution (e.g. as its ammonium salt). In apreferred embodiment the reaction mixture is directly used in thefollowing reaction step.

In a further process of the invention a herbicidal imidazolinonecompound (IV) is prepared by a process comprising the steps of

-   (i) preparing an amido compound of formula (V); and-   (ii) reacting compound (V) with CH₃OM or MOH/CH₃OH (where M is    alkali metal, preferably Na or K) followed by acidification to form    the herbicidal imidazolinone (IV).

In one embodiment, in step (ii) amido compound (V), preferably in theform of an ammonium salt (R³ is HNR₃), is reacted with an alkali metalmethoxide, preferably NaOCH₃ in methanol in analogy to example 11 of EP0 322 616. The resulting suspension is held at reflux until completeconversion. After cooling the mixture is acidified to obtain compound(IV) either as the ammonium salt (acidification to a pH of about 4) orthe free acid (acidification to pH≦2).

In a further preferred embodiment, in step (ii) the reaction mixturefrom step (i) is reacted with methanol (generally 2 to 100 equivalentsbased on (V)) in the presence of an aqueous base (generally 3 to 100equivalents based on (V)), the base being preferably selected from MOHand MOCH₃, where M is an alkali metal, preferably Na or K, particularlyNa.

The reaction is carried out at a temperature in the range of from 20 to120° C., preferably 40 to 90° C. The reaction can be carried out atatmospheric pressure or at elevated pressure, preferably the pressureforming at the desired reaction temperature. The reaction time isgenerally from 1 to 8 h, preferably from 1 to 5 h.

Isolation of imidazolinone product (IV) can be achieved by standardmethods. In a preferred embodiment water is added and organic solventsare distilled off. The residue can be taken up in water and acidified,whereupon compound (IV) precipitates. After filtration the crude productcan be further purified, e.g. by stirring with water orrecrystallization.

In a further embodiment of the invention there is provided a process forpreparing herbicidal imidazolinones of formula (IV) comprising the stepof

-   (i) reacting compound (I) with a base selected from MOH and MOCH₃,    where M is alkali metal, and (aqueous) H₂O₂ in methanol, optionally    followed by acidification.

The reaction may be carried out in analogy to the procedures describedin EP-A 0 144 595.

EXAMPLES

The invention is illustrated by the following examples without limitingit thereby.

Example 1 Synthesis of2-[(1-cyano-1,2-dimethylpropyl)carbamoyl]-5-chloromethyl nicotinic acid(Ia)

9.6 g (48 mmol) 5-chloromethyl-pyridine-2,3-carboxylic acid anhydride(IIa), 40.0 g (435 mmol) toluene and 6.7 g (112 mmol) acetic acid werecharged to a reactor and heated up to 69° C. 7.2 g (51 mmol)α-amino-1,2-dimethyl-butyronitrile were added over 25 min at atemperature between 72° C. and 76° C. The mixture was stirred foradditional 90 min at 75° C. After cooling the mixture can be directlyused for hydrolysis of the nitrile.

Example 2 Synthesis of Imazamox (IVa) (a) Synthesis of2-[(1-carbamoyl-1,2-dimethylpropyl)carbamoyl]-5-chloromethyl nicotinicacid (Va)

To 14.9 g (48 mmol) nitirile (Ia) (from example 1), 6.0 g (59 mmol)sulfuric acid (98%) was added at 69° C. to 80° C. within 5 min. 4.1 g(228 mmol) water was added at 70° C. to 78° C. and stirring continued at69° C. for 5 h. The emerging product forms a toluene insoluble oil. Thereaction mixture was used without workup in the following stage.

(b) Synthesis of Imazamox (IVa)

To 15.7 g (48 mmol) amido compound (Va) (reaction mixture from stage(a)) 94 g (2.94 mol) methanol was added at 65° C. and subsequently 42 g(525 mmol) NaOH (50% in water). The solution turned into a suspension,and stirring was continued for additional 90 min.

80 g water was added and solvents were removed at 50° C. and 80-8 mbar.Residue was dissolved in water and the basic solution acidified with 29g sulfuric acid (98%). Imazamox precipitated from pH 4 on. Thesuspension was filtered at room temperature and washed with 100 mlwater.

Yield: 16.5 g (82% pure, 44 mmol, 92%)

Purity was enhanced to >95% (HPLC) by stirring the crude product withwater.

Example 3 Synthesis of 5-chloromethyl-2,3-pyridine dicarboxylic acidanhydride (IIa)

106.8 g (0.65 mol) of 5-methyl-2,3-pyridine dicarboxylic acid anhydridewere dissolved in 427 g chlorobenzene and heated up to 85° C. A solutionof 0.64 g (0.004 mol) AlBN in 99.0 g (0.66 mol) SO₂Cl₂ was added during45 min. The mixture was stirred for additional 90 min at 85° C.Chlorobenzene was partly distilled off and the solution was cooled to10° C. via 10 h ramp. The precipitate was filtered off and washed withchlorobenzene/hexane.

Yield: 85.0 g (0.40 mmol, 60%) of which 58.1 g (0.27 mmol) could beisolated after precipitation.

The invention claimed is:
 1. A compound of formula (I),

wherein Z is hydrogen or halogen; Z¹ is hydrogen, halogen, cyano ornitro; R¹ is C₁-C₄ alkyl; R² is C₁-C₄ alkyl or C₃-C₆ cycloalkyl or R¹and R² together with the atom to which they are attached form a C₃-C₆cycloalkyl group optionally substituted with methyl, and R³ is hydrogenor a cation.
 2. The compound of claim 1, wherein Z and Z¹ are H.
 3. Thecompound of claim 1, wherein R¹ is CH(CH₃)₂ and R² is CH₃.
 4. Thecompound of claim 1, wherein Z and Z¹ are H R¹ is CH(CH₃)₂; R² is CH₃and R³ is H.
 5. A process for preparing the compound of claim 1,comprising: (i) reacting a compound of formula (II),

wherein, with a 2-aminoalkane carbonitrile (III),H₂N—CR¹R²—CN  (III) to obtain a compound of formula (I).
 6. The processof claim 5, wherein the ratio of the compound formula of (II) to thecompound of formula (III) is 1:0.8-1.2.
 7. The process of claim 5,wherein said reacting of the compound of formula (II) with the compoundof formula (III) is carried out in a solvent selected from the groupconsisting of aromatic hydrocarbons, chlorinated aromatic hydrocarbons,chlorinated aliphatic hydrocarbons, acetic acid, and mixtures thereof.8. The process of claim 5, wherein either acetic acid is the solvent or0.5 to 10 equivalents of acetic acid (based on (II)) are added to thesolvent.
 9. The process of claim 5, wherein the reaction is carried outat a temperature in the range of from 40 to 120° C.
 10. The process ofclaim 5, wherein the reaction mixture is essentially free of pyridine,picolines and quinoline.
 11. The process of claim 5, further comprising(i-1) reacting a compound of formula (VI),

with a chlorinating agent, optionally in the presence of a radicalinitiator in a solvent selected from halogenated hydrocarbons, (i-2)crystallizing the compound (II) formed in step (i) from a solventselected from the group consisting of 1,2-dichloroethane, chlorobenzene,1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene,trichloromethane, dichloromethane, toluene, xylenes, mesitylenes, alkylacetates (e.g. ethyl acetate, butyl acetate, methyl acetate), methyltert.-butyl ether, diisopropylether, cyclopentyl methyl ether, andmixtures thereof, to obtain anhydride (II), and (i-3) reacting anhydride(II) with a 2-aminoalkane carbonitrile (III),H₂N—CR¹R²—CN  (III) to obtain a compound of formula (I).
 12. A processfor manufacturing an amide of formula (V),

wherein Z is hydrogen or halogen; Z¹ is hydrogen, halogen, cyano ornitro; R¹ is C₁-C₄ alkyl; R² is sC₁-C₄ alkyl or C₃-C₆ cycloalkyl or R¹and R² together with the atom to which they are attached form a C₃-C₆cycloalkyl group optionally substituted with methyl, and R³ is hydrogenor a cation; comprising (i) hydrolyzing the compound of claim 1 toobtain an amide of formula (v).
 13. A process for preparing a herbicidalimidazolinone compound of formula (IV),

wherein Z is hydrogen or halogen; Z¹ is hydrogen, halogen, cyano ornitro; R¹ is C₁-C₄ alkyl; R² is C₁-C₄ alkyl or C₃-C₆ cycloalkyl or R¹and R² together with the atom to which they are attached form a C₃-C₆cycloalkyl group optionally substituted with methyl, and R³ is hydrogenor a cation; comprising (i) hydrolyzing the compound of claim 1 toobtain an amide of formula (V), and (ii) reacting compound (V) withCH₃OM or MOH/CH₃OH (where M is alkali metal), optionally followed byacidification to form the herbicidal imidazolinone (IV).
 14. The processof claim 13, further comprising (i-1) preparing the compound of formula(I) by reacting an anhydride of formula (II)

wherein Z is hydrogen or halogen; Z¹ is hydrogen, halogen, cyano ornitro; with an aminonitrile (III)H₂N—CR¹R²—CN  (III), wherein R¹ is C₁-C₄ alkyl; R² is C₁-C₄ alkyl, C₃-C₆cycloalkyl or R¹ and R² together with the atom to which they areattached form a C₃-C₆ cycloalkyl group optionally substituted withmethyl and (i-2) hydrolyzing the compound of formula (I) thus obtainedto yield an amido compound of formula (V)